Skip to content
This repository has been archived by the owner on Sep 23, 2024. It is now read-only.

Draft: Calculate max/min for DECIMAL columns #108

Open
wants to merge 1 commit into
base: master
Choose a base branch
from
Open

Draft: Calculate max/min for DECIMAL columns #108

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
15 changes: 15 additions & 0 deletions tap_mysql/discover_utils.py
View file
Open in desktop
Original file line number Diff line number Diff line change
@@ -1,6 +1,8 @@
# pylint: disable=missing-docstring,too-many-locals

import collections
from decimal import Decimal, BasicContext, localcontext, Context

import itertools
import pendulum
import pymysql
Expand Down Expand Up @@ -269,6 +271,19 @@ def schema_for_column(column): # pylint: disable=too-many-branches

if data_type == 'decimal':
result.multipleOf = 10 ** (0 - column.numeric_scale)
# This is complex.
# Emax specifies the maximum allowable exponent.
# For example, with 10 digits, 3 after decimal place (7 before) we have:
# >>> setcontext(Context(prec=10, Emax=7))
# >>> Decimal('1.0E+7').next_minus()
# Decimal('9999999.999')
before_dp = column.numeric_precision-column.numeric_scale
with localcontext(Context(Emax=before_dp, prec=column.numeric_precision)):
largest_decimal = Decimal('1.0E+' + str(before_dp)).next_minus()

result.maximum = float(largest_decimal)
Copy link
Contributor Author

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

I think this should probably be configurable; by default the old behavior can be kept, but if you opt in to schema_includes_decimal_max_min config then this would be conditionally enabled.

Without a config flag, it'll be backwards-incompatible and will break existing target-schemas.

# TODO: Unsigned.
result.minimum = float(-largest_decimal)

elif data_type in JSON_TYPES:
result.type = ['null', 'object']
Expand Down
15 changes: 12 additions & 3 deletions tests/integration/test_tap_mysql.py
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -83,7 +83,10 @@ def test_decimal(self):
self.assertEqual(self.schema.properties['c_decimal'],
Schema(['null', 'number'],
inclusion='available',
multipleOf=1))
multipleOf=1,
maximum=float('9'*10), # Default is DECIMAL(10,0)
minimum=-float('9'*10),
))
self.assertEqual(self.get_metadata_for_column('c_decimal'),
{'selected-by-default': True,
'sql-datatype': 'decimal(10,0)',
Expand All @@ -93,7 +96,10 @@ def test_decimal_unsigned(self):
self.assertEqual(self.schema.properties['c_decimal_2_unsigned'],
Schema(['null', 'number'],
inclusion='available',
multipleOf=0.01))
multipleOf=0.01,
maximum=float('9'*3 + '.99'),
minimum=0
),)
self.assertEqual(self.get_metadata_for_column('c_decimal_2_unsigned'),
{'selected-by-default': True,
'sql-datatype': 'decimal(5,2) unsigned',
Expand All @@ -103,7 +109,10 @@ def test_decimal_with_defined_scale_and_precision(self):
self.assertEqual(self.schema.properties['c_decimal_2'],
Schema(['null', 'number'],
inclusion='available',
multipleOf=0.01))
multipleOf=0.01,
maximum=float('9'*9 + '.99'),
minimum=-float('9'*9 + '.99'),
))
self.assertEqual(self.get_metadata_for_column('c_decimal_2'),
{'selected-by-default': True,
'sql-datatype': 'decimal(11,2)',
Expand Down